Ok, the first step is to find the TxnID of the Bill Payment Check. In this example I know that the check number is 276, so I run the following query:

Select TxnID, RefNumber, BankAccountRefFullName, Amount from BillPaymentCheckLine
where RefNumber = '276'

Now that I know that the TxnID is '36C3-1071520917', I can run the following report to extract all the voucher details:

sp_report CheckDetail show TxnType, RefNumber, Date, Name, Item, Account,
SplitAccount, PaidAmount, OriginalAmount
parameters DateMacro = 'ThisMonthToDate', TxnFilterTypes = 'BillPaymentCheck'
where TxnID = '36C3-1071520917'